Flexible jointed drill pipe



July 27, 1954 J, A ZUBLIN 2,684,581

FLEXIBLE JOINTED DRILL PIPE Filed-Nov. 6, 195] 3 Sheets-Sheet l fw I L JEW- IIIIII IN VENTOR ATTORNEYS J. A. ZUBLIN FLEXIBLE JOINTED DRILL PIPE July 27, 1954 5 Sheets-Sheet 2 Filed NDV 6, 1951 Jaim. ,Mgg

BY QM 9,

July 27, 1954 1. A. zuBLlN FLEXIBLE JOINTED DRILL PIPE 3 SheetsY-Sheet 3 Filed NOV. 6, 195] INVENTOR n/blj l BY wel ATTORNEYS .Av ull I l /J www m w n Patented July 27, 1954 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to a flexible, jointed drill pipe section of the character adapted to be suspended from the lower end of a drill string for use in the drilling of curved bores deviating from existing vertical well bores. It is the purpose and object of the invention to provide a nonresilient, flexible, tubular drill string section of rugged construction capable of flexing within definitely prescribed limits while insuring a positive drive connection between the normally rigid drill string and the bit.

More specifically, it is an object of the invention to provide a nonresilient, flexible, tubular drill string section made up of duplicate interconnected units of predetermined equal length and carrying at one end thereof an externally threaded pin conforming to the conventional pin end of a drill string section and at the opposite end thereof an internally threaded box conforming with the box end of a conventional drill string section.

It is still a further and more specific object of the invention to provide a nonresilient, iiexible, tubular drill string section of substantially uniform exterior diameter throughout its length and which may be incorporated in a rotary drill string without modification of any of the elements thereof.

It is a further and more specific object of the invention to provide a nonresilient, flexible drill string section which is adapted to enter into a curved bore of limited diameter and which may be easily withdrawn from a lateral bore of substantial length.

It is a further and more specific object of the invention to provide a nonresilient, flexible drill string section capable of assuming a predeterh mined uniform radius of curvature.

Further and more detailed objects of the invention will become apparent as the description proceeds, which Will be given in connection with the accompanying drawings wherein Figure 1 is a view in side elevation illustrating the position assumed by the nonresilient drill string section in the drilling of a curved bore deviating from an existing vertical well bore.

Figure 2 is an enlarged detailed View showing a series of sections of the nonresilient drill string section as they appear when at rest and in vertical alignment.

Figure 3 is a fragmentary, detailed, cross-sectional view of the lower end and box of the iiexible drill string section of the invention showing the parts in vertical alignment and at rest.

Figure 4 is a fragmentary, detailed, cross-sectional view through the upper end and pin of the flexible drill string section of the present invention showing the parts in kinked position.

Figure 5 is an enlarged, detailed view illustrating the manner of interengagement of the clutch teeth carried by adjacent ends of the units forming the nonresilient drill string section.

Figure 6 is a cross-sectional View taken on the line li-B of Figure 3 showing the position of the clutch teeth when the adjacent units are in vertical alignment and the drill string section is at rest.

Figure 7 is a cross-sectional View similar to Figure 6 but showing the position assumed by the clutch teeth when a driving force in the direction of the arrow is imparted to the drill string section.

Figure 8 is a cross-sectional view taken on the line 8 8 of Figure 4 showing the position assumed by the clutch teeth when adjacent units are kinked and when a driving force is applied in the direction of the arrows.

Figure 9 is a detailed, cross-sectional View illusstrating the mode of assembly of the units.

Figure 10 is a detailed, cross-sectional view taken on the line IU--I D of Figure 3.

Figure 11 is a detailed, cross-sectional view of a modified individual unit, and

Figure 12 is a cross-sectional view taken on the line l2-l2 of Figure 11.

Referring to Figure 1, the conventional, normally rigid, rotary drill string is indicated at lll. Suspended from the lower end of the drill string IQ is a iiexible, nonresilient, tubular drill string section indicated generally at Il and which is composed of a plurality of individual sections l2, all of uniform length. At the upper end of the flexible drill string section there is a pin connection I3 adapted to be threadedly received in the lower end of the rotary drill string In and at the lower end of the iiexible drill string section Il there is a box l Il (see Figure 3) adapted to receive either the shank of a bit or the pin of the next succeeding lower drill string section which, in Figure l, is indicated generally at l5 and comprises a second flexible, tubular drill string section of the same construction as the section Il. In Figure 1, the second flexible drill string section l5 is illustrated as extending through the normally curved, resilient, liexible drill guide i6 which acts to guide the bit I1 in the drilling of a deviating bore I8 from an existing vertical well bore IS. rIhe normally curved, resilient flexible drill guide may be of the type described in my prior United States Patent No. 2,336,338. The

over-all length of the pin I3 and box I4 should not exceed the length of one of the units I2 since, when two flexible drill string sections such as I I and I5 are interconnected, the point of union will not disturb the over-all flexibility of the assembly.

Referring now to Figures 3 and 4 which respectively represent the upper and lower portions of the flexible drill string section II, it will be observed that each of the units i2 embraces an outer female member having annularly disposed clutch teeth 2l at its upper end and interiorly threaded at its lower end at 22. A male member 23 carrying external threads 24 and internal threads 25 has its external threads 24 received in the interior threads 22 of 'the female member 25. A weld 25 is positioned between the shoulder 21 on the male member and the free end 28 of the female member. A packing 29 extends coaxially with the female member 20 and male member 23 and is normally carried on the reduced portion 30 of the male member 23 above the shoulder 3I. Complemental socket-forming surfaces 32 and 33 are formed respectively on the interior wall of the female member .23 at the upper end of the male member 23. The packing 29 intersects the socket formed between surfaces 32. and 33 and has its upper end 34 conformed with the wall of the socket. A hollow ball member 35 having a central opening 35 is seated in the socket formed by the surfaces 32, 33 and 34. The hollow ball member 35 has the upwardly projecting tubular extension 31 that projects well above the clutch teeth 2l carried by the female member 20 and is exteriorly threaded as indicated at 38. The bore or central opening 36 extends through the ball member 35 and the integral tubular extension 31 and is always in substantial alignment with the bore 4B. in the male member 23 and provides a free passageway for circulating drilling fluid through the unit. The upper end of the tubular female section 2l! has an outwardly flared collar portion 4I and the interior surface flares outwardly from the longitudinal axis of the female member 20 and the unit at an angle not exceeding eight and prefererably about four and one-half degrees. Thus, the hollow ball 35 and its tubular extension 31 have free pivotal movement in all directions in the socket formed by the surfaces 32, 33 and 34 within the limits of said four and one-half degree angle which, it will be appreciated, restricts the extent of flexibility of the nonresilient, flexible, drill string section II. The male member 23 at its lower end carries spaced, annularly disposed clutch teeth 42 which are adapted to engage the spaced, annularly disposed clutch teeth 2I at the upper end of the female member 2li in the next adjacent unit.

In the assembly of each unit, the clutch teeth 42 at the lower end of the male member 23 are longitudinally disaligned with the clutch teeth 2l at the upper end of the female member 2% of that unit. This disalignment is usuallyl about one-half the width of an individual clutch tooth as indicated at a in Figure 2.

It will be appreciated that the female member 26, male member 23 and hollow ball member 35 with its tubular extension 31, together with the associated weld 25 and packing 29, constitute one complete unit such as designated generally at I2 in Figure 1. It will be appreciated that the radius of curvature obtainable will depend on the number of units I2 incorporated in the flexible, tubular drill string section. The upper terminal end of the tubular, drill string section carries pin 43, the interior threads 44 of which receive the exterior threads 38 of the tubular extension 31 of the hollow `ball member 35. The exterior threads 45 of the pin 43 are so formed as to be received in the conventional box of any rotary drill string section.

It will be understood that all of the intermediate sections I2 of the flexible, tubular drill string section are of identical construction and that the respective elements are interchangeable and may be easily replaced when worn or damaged. The manner of assembly will be best appreciated by reference to Figures 9 and l0. Referring to Figure 9, it will be noted that the bore 36 of the hollow ball member 35 has a keyway 4S formed at one side thereof. This keyway is provided for the reception of the key 41 carried on the pin 48 of the tool 49. When the clutch teeth 4?. of the male member 23 of an upper unit are brought into engagement with the clutch teeth 2i of the next-to-be assembled female member 25 the hollow ball member 35 is placed on the tool 43l with the key 41 thereof extending into the keyway 4S. The female member 2i] is then placed over the hollow ball member 35 and its tubular extension 31 and the tool 4S rotated to interengage the threads 38 of the tubular extension 31 of the hollow ball member 35 with the interior threads 25 of the male member 23 in the next adjacent unit. The tool 4S can then be removed and a male member 23 carrying a packing 2S inserted in the open end of the female member 25 with the exterior threads 24 thereof engaging the interior threads 22 of the female member 20. The surface 34 of the packing 29y is thus brought into contact with the exterior surface of the hollow ball member 35 and the relative axial movement between the female member 20 and the male member 23 provides means for insuring a pressure-tight joint between the ball and socket. When the male member 23 is threaded home in the female member 2G and the clutch teeth 42 properly disaligned with clutch teeth 2 I, the weld 26 is applied.

Since the units I2 are all duplicates it is unnecessary to describe more than one of them.

The lowermost unit I2 of the flexible drill string section, however, receives a box indicated generally at I4 (see Figure 3). This box is provided with a shoulder 5l] and a portion of reduced diameter 5I for carrying a packing 52 in all respects the same as the packing 29 so that when the box I4 is screwed into the threads 22 of the outer female member of the lowermost unit I2 the packing 52V will be forced into contact with the outer surface of the hollow ball 35 in the same manner as the surface 34 of the packing 29 is forced into contact with the outer surface of the hollow ball portion 35. The interior threads 53 of the box I4 are so formed as toreceive the pin of another drill string section or to receive the sub of a bit such as the bit I1.

The unit disclosed in Figures ll and 12 differs only from the units heretofore described in that instead of providing the opening' 35 in the hollow ball portion 35 with a keywa-y 45,y the opening in the ball indicated at 54 in Figure ll is provided with a square opening 55 and in this form the assembly will be effected by a modified form of the tool 49 provided with a square shank adapted to be received in the square opening 55 of the ball 54.

It is an important feature of the invention that the clutch teeth 2I carried by the female member 20 and clutch teeth 42 carried by the male member 23 are tapered from their respective bases toward their free ends. I have found that this particular construction is highly advantageous in permitting a continuous, even rotation of the units making up the over-all nonresilient drill string section, more particularly when it is rotated in a curved bore as will be readily understood when the adjacent units I2 assume a kinked position on entering a curved bore such as shown in Figure 1 and accentuated in Figure 3. The teeth at the inside of the curvature will be engaged while the teeth at the outside will be separated. This is well exemplified in Figure 8 of the drawings. When the unit is rotated the teeth which were first on the inside of the curvature move around to the outside of the curvature and in so doing are separated. By virtue of the tapered form of the clutch teeth 2l and 2, they are .permitted to pass from driving engagement to nonengagement while maintaining the angle of deviation of four and one-half degrees at each joint without interfering with the ball and socket motion. Through this structure the units are permitted to pass from longitudinal alignment into kinked positions without any jarring or shaking motion of the assembly. When the adjacent units are in kinked position such as shown in Figure 8, there is engagement between only one driving and one driven clutch tooth.

Referring to the pressure diagram of Figure 5, adjacent clutch teeth will, upon contact and under the driving force P, develop a triangle of forces indicated at PI-PZ-PB. Forces P and PI are equal and force P2 is at right angles to the tooth surface. Thus, force P3 tends to axially separate the two teeth. Axial separation of juxtaposed teeth will, of course, reduce the angle of four and one-half degrees and eventually to no angle whatever. When this happens, however, all of the driving clutch teeth 42, for example, engage all of the driven clutch teeth 2|, for example, as indicated in Figure 7, at which time the force P3 is the same for all of the teeth that are in engagement. spaced about the circumference of the units, they fully compensate each other. The tapered teeth actually function to straighten out the assembly made up of the jointed units Whenever that is possible.

It will thus be seen that the exible, nonresilient drill string section of the present invention will remain straight under normal conditions when it is being introduced into a straight bore. An increase in torque and pressure applied to the drill .string will increase in proportion the tendency of the same to straighten out. By way of exemplication it is preferred that the teeth be tapered from their bases to their free ends at an angle of about 60 degrees. It will be appreciated that when the nonresilient, flexible drill string section is introduced into a curved bore the deviation forces of the wall of the curved bore will be greater than the tendency of the nonresilient, flexible drill string section to straighten out. The straightening eect will thus take place only where it is most needed, that is, in a straight, vertical bore or in a straight continuation of a curved bore.

The disalignment of the clutch teeth at opposite ends of each unit I2 of the nonresilient ilexible drill string section l is also a matter of importance. Unavoidably, there is a certain blow imparted when two clutch teeth are brought into disengagement and then out of engagement.

Since the teeth are equally The staggered relation of the clutch teeth at opposite ends of the units prevents a simultaneous blow as a result of engagement and disengagement of clutch teeth at opposite ends of the given unit at the same time. By staggering the position of the clutch teeth through disalignment, the rotation of the nonresilient, flexible drill string section in a curved bore is made much more steady and uniform with greater freedom of shock than is otherwise possible.

It is an important feature of the invention that the flexible, tubular drill string section of the invention permits the employment of pump pressures of the order of 1500 pounds on the circulating lfluid passed through the flexible drill string section.

From the foregoing description it will be appreciated that I have provided a very simply constructed, flexible, tubular drill string section by which the radius of curvature obtainable may be accurately controlled and which is highly effective in use. Each unit is comprised of three basic elements, all of which are replaceable and readily exchangeable with like elements of other similar units which greatly lends to the economy of production and upkeep of the iiexible, tubular drill string section. The flexible tubular drill string section can be operated not only as shown in the drawings, but also in inverted position with the end pin I3 at the lower end and the box I4 at the upper end.

Having thus described my invention, what I claim is:

1. A flexible tubular drill pipe section embracing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth annularly disposed about one end thereof, a tubular male member threadedly received in the opposite end of said female member, clutch teeth annularly disposed about the free end of said male member, a socket formed jointly in the opposed surfaces of said male and female members, an annular packing extending ooaxially for a substantial distance between said members having its upper end conformed to the vwall of said socket, a hollow ball member seated in said socket and having a tubular extension projecting beyond said clutch teeth carried by said female member, means intercom necting said tubular extension and the male member of the next adjacent unit, a hollow externally threaded pin at one end of said ilexible tubular pipe section and a hollow internally threaded box at the opposite end of said ilexible tubular pipe section.

2. A exible tubular drill pipe section en'ibracu ing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth annularly disposed about one end thereof, a tubular male member threadedly received in the opposite end of said female member, clutch teeth annularly disposed about the free end of said male member, a socket formed jointly in the opposed surfaces of said male and female members, an annular packing extending coaxially for a substantial distance between said members having its upper end conformed to the wall of said socket, a hollow ball member seated in said socket and having a tubu lar extension projecting beyond said clutch teeth carried by said female member, means interconnecting said tubular extension and the male member of the next adjacent unit, the inner wall of the upper portion of said female member flaring outwardly at an angle to its longitudinal axis not exceeding eight degrees to permit free pivotal movement of said ball in said socket within the limits of said angle, a hollow externally threaded pin at one end of said exible tubular pipe section and a hollen7 internally threaded box at the opposite end of said flexible tubular pipe section.

3. A flexible tubular pipe section embracing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth annularly disposed about one end thereof, a tubular male member having both external and internal threads, the external threads thereof received in the opposite end of said female member, clutch teeth annularly disposed about the free end of said male member, a socket formed jointly in the adjacent surfaces of said male and female members, a hollow ball member seated in said socket and having an externally threaded tubular extension projecting beyond said clutch teeth carried by said female member, the external threads of said tubular extension of said ball member of one unit being threadedly received in the internal threads of the male member of the next adjacent unit, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

e. A flexible tubular drill pipe section embracing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about one end thereof, a tubular male member threadedly received in the opposite end of said female member, clutch teeth substantially tapered from their bases toward their free ends. annularly disposed about the free end of said male member, a socket formed jointly in the opposed surfaces of said male and female members, an annular packing extending coaxially for a substantial distance between said members having its upper end conformed to the wall of said socket, a hollow ball member seated in said socket and having a tubular extension projecting beyond said clutch teeth carried by said female member, means interconnecting said tubular extension and the male member of the next adjacent unit, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

5. A flexible drill pipe section embracing a plurality of interconnected units, each unit comprising an outer female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about one end thereof, a male member threadedly received in the opposite end of said female member', clutch teeth substantially tapered from their bases toward their free ends annularly disposed about the free end of said male member, a socket wholly within said female member, said socket being spaced longitudinally from the bases of said clutch teeth carried by said female member, a ball member seated in said socket and having a unidirectional extension projecting beyond said clutch teeth carried by said female member, means interconnecting said tubular extension and the male member of the next adjacent unit, the inner wall of the upper portion of said female member flaring outwardly at an angle to its longitudinal axis to permit free pivotal movement of said ball in said socket within the limits of said angle.

6. A flexible tubular pipe section embracing a yplurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about one end thereof, a. tubular male member having both external and internal threads, the external threads thereof received in the opposite end of said female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about the free end of said male member, a socket formed jointly inthe adjacent surfaces of said male and female members, a hollow ball member seated in said socket and having an externally threaded tubular extension projecting beyond said clutch teeth carried by said female member, the external threads of said tubular extension of said ball member of one unit being threadedly received in the internal threads of the male member of the next adjacent unit, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

7. A flexible tubular drill pipe section embracing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth substantially tapered from their' bases toward their free ends annularly disposed about one end thereof, a tubular male member threadedly received in the opposite end of said female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about the free end of said male member, the clutch teeth on said female member and the clutch teeth on said male member being longitudinally disaligned, a socket formed jointly in the opposed surfaces of said male and female members, an annular packing extending coaxially for a substantial distance between said members having its upper end conformed to the wall of said socket, a hollow ball member seated in said socket and having a tubular extension projecting beyond said clutch teeth carried by said female member, means interconnecting said tubular extension and the male member of the next .adjacent unit, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

8. A flexible tubular drill pipe section embracing a plurality of interconnected units of equal length, each unit comprising an outer tubular female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about one end thereof, tubular male member threadedly received in the opposite end of said female member, clutch teeth substantially tapered from their bases toward their ee ends annularly disposed about the free end or" said male member, the clutch teeth on said female member and the clutch teeth on said male member being longitudinally disaligned, a socket formed jointly in the opposed surfaces of said male and female members, an annular packing extending coaxially for a substantial distance between said members having its upper end conformed to the wail of said socket, a hollow ball member seated in said socket and having a tubular extension projecting beyond said clutch teeth carried by said female member, means interconnecting said tubular extension and the male member of the next adjacent unit, the inner wall of the upper portion of said female member flaring outwardly at an angle to its longitudinal axis not exceeding eight degrees to permit free pivotal movement of said ball in said socket within the limits of said angle, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

9. A exible tubular pipe section embracing a plurality of interconnected units of equal length, each unit eomprsing an outer tubular female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about one end thereof, a tubular male member having both external .and internal threads, the external threads thereof received in the opposite end of said female member, clutch teeth substantially tapered from their bases toward their free ends annularly disposed about the free end of said male member, the clutch teeth on said female member and the clutch teeth on said male member being lonl0 gitudinally disaligned, a socket formed jointly in the adjacent surfaces of said male and female members, a hollow ball member seated in said socket and having an externally threaded tubular extension projecting beyond said clutch teeth carried by said female member., the external threads of said tubular extension of said ball member of one unit being threadedly received in the internal threads of the male member of the next adjacent unit, a hollow externally threaded pin at one end of said flexible tubular pipe section and a hollow internally threaded box at the opposite end of said flexible tubular pipe section.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 829,977 Lockwood Sept. 4, 1906 FOREIGN PATENTS Number Country Date 15,259 Great Britain 1889 485,872 France l- Nov. 23, 1917 

